JP2005169600A - drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain good chip discharge performance.
A cutting edge portion 12 is connected to a polishing margin portion 16 whose core thickness is substantially constant along the axis O direction and a rear end of the polishing margin portion 16 and has a core thickness in the axis O direction. A back taper portion 17 that gradually decreases toward the rear end side, and a straight portion 18 that is continuous with the rear end of the back taper portion 17 and whose core thickness is substantially constant along the axis O direction. To. The core thickness at the tip of the back taper portion 17 is set in the range of 0.25D to 0.40D with respect to the outer diameter D of the cutting blades 15 and 15, and the core thickness at the rear end of the back taper portion 17 is The cutting edges 15 and 15 are set in a range of 0.20D to 0.25D with respect to the outer diameter D.
[Selection] Figure 1

Description

  The present invention relates to a drill used for drilling for forming a processed hole in a work material, for example, a drill used for forming a deep hole processed hole.

Conventionally, a pair of chip discharge grooves extending toward the rear end side are formed on the outer periphery of the cutting edge part, which is the tip side part of the drill body rotated about the axis, and these chips discharge grooves face the front side in the drill rotation direction. There is known a drill in which a cutting edge is formed at an intersecting ridge line portion between an inner wall surface and a tip flank surface of a blade edge portion. Further, in such a drill, the core thickness gradually decreases with a constant change trend toward the rear end side in the axial direction over the entire length of the cutting edge (for example, Patent Document 1). reference).
JP 2003-94220 A (FIG. 2)

In the conventional drill described above, the core thickness of the cutting edge portion is gradually decreased with a constant change tendency toward the rear end side in the axial direction, that is, the space of the chip discharge groove formed in the cutting edge portion is reduced to the rear end side. By gradually increasing in a constant changing direction, it is intended to ensure chip dischargeability particularly at the rear end side portion of the blade edge portion where chip clogging is likely to occur.
However, since the core thickness of the cutting edge portion only gradually decreases with a constant change tendency toward the rear end side over the entire length of the cutting edge portion, the chips generated from the cutting edge during drilling processing, There are many cases where clogging occurs in the chip discharge groove before reaching the rear end side portion of the cutting edge where a large space for the chip discharge groove is secured, and the drill as described above maintains good chip discharge performance. The current situation is that it cannot be an effective solution for this. Such a tendency becomes prominent particularly in a drill used for forming a deep hole, that is, a drill in which the entire length of the cutting edge is set long.

  This invention is made | formed in view of the said subject, and it aims at providing the drill which can keep chip | tip discharge | emission property favorable.

  In order to solve the above problems and achieve such an object, the present invention provides a chip discharge extending toward the rear end side on the outer periphery of the cutting edge portion which is the front end side portion of the drill body rotated about the axis. In the drill in which a groove is formed and a cutting edge is formed at an intersecting ridge line portion between the inner wall surface facing the front side of the drill rotation direction of the chip discharge groove and the tip flank of the cutting edge portion, the cutting edge portion has a core thickness. Is a back taper portion that gradually decreases as it goes toward the rear end side in the axial direction, and a straight portion that is continuous with the rear end of the back taper portion and whose core thickness is substantially constant along the axial direction. It is characterized by having.

In such a drill according to the present invention, the core thickness of the cutting edge portion is not gradually decreased toward the rear end side over the entire length of the cutting edge portion as in the conventional case, but at the back taper portion at the rear end side. After the sharp decrease to the straight portion, the straight portion is kept constant, that is, after the space of the chip discharge groove is increased rapidly toward the rear end side in the back taper portion, the straight portion Is kept constant at
For this reason, the chips generated from the cutting edge during drilling are first curled small and compactly at the tip of the cutting edge where the chip discharge groove space is set small, and then the chips are discharged immediately. The rear end of the back taper portion where the groove space is set large is reached. The chips that have reached the rear end of the back taper portion are smoothly guided toward the rear end in the chip discharge groove of the straight portion where the space of the chip discharge groove is set as it is.
Therefore, a drill in which the length along the axial direction in the cutting edge portion is set in a range of 8.0D to 30.0D with respect to the outer diameter D of the cutting edge, that is, deep hole machining. Even in the case of drilling using a drill for forming a hole, it is possible to keep the chip discharge performance good.

  Further, regarding the back taper portion of the blade edge portion, considering the effect of maintaining good chip discharge performance, the rigidity of the blade edge portion, and the like, the core thickness at the tip is 0. 0 relative to the outer diameter D of the cutting edge. The core thickness at the rear end is set in the range of 0.20D to 0.25D with respect to the outer diameter D of the cutting edge, and the length along the axial direction is set in the range of 25D to 0.40D. Is preferably set in a range of 2.0D to 5.0D with respect to the outer diameter D of the cutting blade.

Furthermore, it is preferable that the blade edge portion includes a polishing margin portion that is continuous with the tip of the back taper portion and whose core thickness is substantially constant along the axial direction.
With this configuration, when the cutting edge wears out, the core thickness at the tip of the cutting edge changes even if the cutting edge is re-polished and the cutting edge is re-polished. Therefore, the re-grinding of the tip flank does not affect the chip discharge performance.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
As shown in FIGS. 1 and 2, the drill body 10 of the drill according to the present embodiment is formed in a substantially cylindrical shape centering on the axis O with a hard material such as cemented carbide, and the rear end side portion thereof is a work piece. The shank portion 11 is held by the rotating shaft of the machine, and the tip side portion is the cutting edge portion 12.

  A pair of chip discharge grooves 14 and 14 that are twisted toward the rear side in the drill rotation direction T at a constant twist angle from the tip flank 13 toward the rear end side in the axis O direction are symmetrical with respect to the axis O on the outer periphery of the cutting edge portion 12. The cutting edges 15 and 15 are formed in the intersection ridgeline part of the inner wall surface which faces the drill rotation direction T front side of these chip discharge grooves 14 and 14, and the front-end | tip flank 13, respectively.

The blade edge portion 12 is smoothly connected to the polishing margin portion 16 whose core thickness is substantially constant along the axis O direction and the rear end of the polishing margin portion 16, and the core thickness thereof is the axis O direction. A back taper portion 17 that gradually decreases as it goes toward the rear end side, and a straight portion 18 that is smoothly connected to the rear end of the back taper portion 17 and whose core thickness is substantially constant along the direction of the axis O. I have. The core thickness of the blade edge portion 12 is a circle centered on the axis O inscribed in the cross section of the blade edge portion 12 as shown in FIG. 2 when the blade edge portion 12 is viewed in a cross section perpendicular to the axis O. This is the outer diameter of a circle indicated by a broken line in FIG.
Further, the length L (effective blade length of the blade edge portion 12) along the direction of the axis O in the blade edge portion 12 is the outer diameter D of the cutting blades 15 and 15 (around the axis O about the outer peripheral ends of the cutting blades 15 and 15). The outer diameter of the circle formed by the rotation locus is set in a range of 8.0D to 30.0D.

The core thickness of the grinding allowance portion 16 of the blade edge portion 12 is a substantially constant value over substantially the entire length along the axis O direction from the tip (tip of the blade edge portion 12) to the rear end (tip of the back taper portion 17). The core thickness d1 of the polishing margin 16 is set in a range of 0.25D to 0.40D with respect to the outer diameter D of the cutting blades 15 and 15. That is, the core thickness of the portion from the II cross section to the II-II cross section in FIG. 1 is d1.
Further, the length L1 along the direction of the axis O in the polishing margin 16 is set to a range of 2.0D to 3.0D with respect to the outer diameter D of the cutting blades 15 and 15.

The core thickness of the back taper portion 17 of the blade edge portion 12 is set to d1 at the tip (the rear end of the polishing margin portion 16), and gradually decreases with a constant change trend toward the rear end side in the axis O direction. (E.g., decreasing at a rate of 1.0 / 100) and d2 at the rear end, and the core thickness d1 at the front end of the back taper portion 17 is equal to that of the cutting edges 15 and 15 as described above. The core thickness d2 at the rear end of the back taper portion 17 is set to a range of 0.25D to 0.40D with respect to the outer diameter D, and is 0.20D to with respect to the outer diameter D of the cutting blades 15 and 15. The range is set to 0.25D. That is, the core thickness of the portion from the II-II cross section to the III-III cross section in FIG. 1 gradually decreases from d1 to d2.
In addition, the length L2 along the axis O direction in the back taper portion 17 is set in a range of 2.0D to 5.0D with respect to the outer diameter D of the cutting blades 15 and 15.

The core thickness of the straight portion 18 of the blade edge portion 12 is substantially constant over substantially the entire length along the axis O direction from the tip (rear end of the back taper portion 17) to the rear end (rear end of the blade edge portion 12). The core thickness d2 of the straight portion 18 is set in the range of 0.20D to 0.25D with respect to the outer diameter D of the cutting blades 15 and 15, as described above. That is, the core thickness of the portion from the III-III cross section to the IV-IV cross section in FIG. 1 is d2.
Further, the length L3 along the axis O direction in the straight portion 18 is appropriately set according to the length L along the axis O direction in the cutting edge portion 12, that is, according to the required depth of the processed hole. Set as appropriate.

  The drill according to the present embodiment configured as described above is cut at the tip of the blade edge portion 12 by feeding the drill body 10 toward the tip side in the direction of the axis O while rotating around the axis O. A work material is cut by the blades 15 and 15 to form a machining hole in the work material. Chips generated from the cutting blades 15 and 15 pass through the chip discharge grooves 14 and 14. It is guided toward the rear end side in the direction of the axis O.

Here, in the present embodiment, the core thickness of the blade edge portion 12 is not gradually reduced toward the rear end side over the entire length of the blade edge portion 12 as in the prior art, but the rear end of the polishing margin portion 16. In the back taper portion 17 connected to the end, after being rapidly decreased toward the rear end side, the straight portion 18 is kept constant.
That is, after the space occupied by the chip discharge grooves 14, 14 formed on the outer periphery of the blade edge portion 12 is rapidly increased toward the rear end side in the back taper portion 17 connected to the rear end of the polishing margin portion 16, The portion 18 is kept constant.

Therefore, the chips generated from the cutting edges 15 during drilling are first small and compact at the tip (polishing margin 16) of the cutting edge 12 where the space for the chip discharge grooves 14, 14 is set small. Immediately thereafter, it reaches the rear end of the back taper portion 17 where the space of the chip discharge grooves 15, 15 is set large.
Then, the chips that have reached the rear end of the back taper portion 17 are left as they are in the chip discharge grooves 14 and 14 of the straight portion 18 where the space of the chip discharge grooves 14 and 14 is set large. It is guided smoothly toward the side.

  Thus, in the drill according to the present embodiment, since the back taper portion 17 whose core thickness is sharply reduced is provided in the blade tip portion 12, smooth chip discharge without causing chip clogging can be realized. A drill for deep hole machining in which the length L along the axis O direction in the portion 12 is set to a range of 8.0D to 30.0D with respect to the outer diameter D of the cutting blades 15 and 15 was used. Even in the case of drilling, the chip discharge performance can be kept good.

Here, the core thickness d1 at the tip of the back taper portion 17 of the blade edge portion 12 (= core thickness d1 of the polishing margin portion 16) is 0.25D to 0.40D with respect to the outer diameter D of the cutting blades 15 and 15. It is preferable that the range is set.
When the core thickness d1 is smaller than 0.25D, the rigidity at the tips of the polishing margin portion 16 and the back taper portion 17 is inadvertently lowered, and the chips generated by the cutting edges 15 and 15 are small and compact. In contrast, if the core thickness d1 is larger than 0.40D, no matter how much the core thickness d2 at the rear end of the back taper portion 17 is set to an appropriate value, There is a possibility that chip clogging may occur at the tips of the polishing margin portion 16 and the back taper portion 17.

Further, the core thickness d2 (= core thickness d2 of the straight portion 18) at the rear end of the back taper portion 17 of the blade edge portion 12 is 0.20D to 0.25D with respect to the outer diameter D of the cutting blades 15 and 15. It is preferable that the range is set.
If the core thickness d2 is smaller than 0.20D, the rigidity of the rear end of the back taper portion 17 and the straight portion 18 is inadvertently lowered, and the processing hole may be bent or the cutting edge portion 12 may be easily broken. Conversely, if the core thickness d2 is greater than 0.25D, smooth chip discharge may not be realized.

Furthermore, the length L2 along the axis O direction in the back taper portion 17 of the blade edge portion 12 is set to a range of 2.0D to 5.0D with respect to the outer diameter D of the cutting blades 15 and 15. preferable.
When the length L2 is smaller than 2.0D, the core thickness of the back taper portion 17 is drastically reduced, and the cutting edge portion 12 may be broken at the connection portion between the back taper portion 17 and the straight portion 18. Conversely, even if the length L2 is greater than 5.0D, the effect of rapidly reducing the core thickness of the back taper portion 17 as described above is diminished.

In addition, in the drill of the present embodiment, the cutting edge portion 12 is provided with a polishing margin portion 16 that is continuous with the tip of the back taper portion 17 and whose core thickness is substantially constant along the axis O direction.
Therefore, even when the cutting edges 15 and 15 are worn as the drilling process continues, even if the tip flank 13 of the cutting edge portion 12 is repolished and the cutting edges 15 and 15 are re-edged, The core thickness at the tip of the blade edge portion 12 does not change. Thereby, even if it compares the drill before re-polishing with the drill after re-polishing, a difference in chip discharge | emission performance does not appear, but it can continue the stable drilling process.

It is a side view of the blade edge | tip part of the drill in embodiment of this invention. It is sectional drawing of the blade edge | tip part of the drill in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Drill main body 11 Shank part 12 Cutting edge part 13 Tip flank 14 Chip discharge groove 15 Cutting edge 16 Polishing margin 17 Back taper part 18 Straight part

Claims (5)

A chip discharge groove extending toward the rear end side is formed on the outer periphery of the cutting edge portion, which is the tip side portion of the drill body rotated about the axis, and the inner wall surface facing the front side in the drill rotation direction of the chip discharge groove and the cutting edge In the drill in which the cutting edge is formed at the intersecting ridge line part with the tip flank of the part,
The blade edge portion is continuous with the back taper portion whose core thickness gradually decreases as it goes toward the rear end side in the axial direction, and the core thickness is substantially along the axial direction. A drill characterized by having a straight portion made constant. The drill according to claim 1,
The core thickness at the tip of the back taper portion is set in a range of 0.25D to 0.40D with respect to the outer diameter D of the cutting blade, and the core thickness at the rear end of the back taper portion is the cutting edge. The drill characterized by being set to the range of 0.20D-0.25D with respect to the outer diameter D of a blade. The drill according to claim 1 or 2,
A length of the back taper portion along the axial direction is set in a range of 2.0D to 5.0D with respect to an outer diameter D of the cutting blade. The drill according to any one of claims 1 to 3,
The length in the said axial direction in the said blade edge | tip part is set to the range of 8.0D-30.0D with respect to the outer diameter D of the said cutting blade, The drill characterized by the above-mentioned. The drill according to any one of claims 1 to 4,
The said blade edge | tip part is equipped with the grinding | polishing margin part which the core thickness was made into substantially constant along the said axial direction while connecting with the front-end | tip of the said back taper part.

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